#!/usr/bin/env python2
###############################################################################
#
# MODULE      : compat.py
# DESCRIPTION : Code from python stdlib for compatibility
#               Should be removed when we upgrade to Python 3

import os
import sys

# Check that a given file can be accessed with the correct mode.
# Additionally check that `file` is not a directory, as on Windows
# directories pass the os.access check.
def _access_check(fn, mode):
    return (os.path.exists(fn) and os.access(fn, mode)
            and not os.path.isdir(fn))

encoding = sys.getfilesystemencoding()

def fsencode(filename):
    if isinstance(filename, str):
        return filename.encode(encoding)
    else:
        return filename

def fsdecode(filename):
    if isinstance(filename, bytes):
        return filename.decode(encoding)
    else:
        return filename

# Extracted from cpython: Lib/shutil.py
def which(cmd, mode=os.F_OK | os.X_OK, path=None):
    """Given a command, mode, and a PATH string, return the path which
    conforms to the given mode on the PATH, or None if there is no such
    file.
    `mode` defaults to os.F_OK | os.X_OK. `path` defaults to the result
    of os.environ.get("PATH"), or can be overridden with a custom search
    path.
    """
    # If we're given a path with a directory part, look it up directly rather
    # than referring to PATH directories. This includes checking relative to the
    # current directory, e.g. ./script
    if os.path.dirname(cmd):
        if _access_check(cmd, mode):
            return cmd
        return None

    use_bytes = isinstance(cmd, bytes)

    if path is None:
        path = os.environ.get("PATH", None)
        if path is None:
            try:
                path = os.confstr("CS_PATH")
            except (AttributeError, ValueError):
                # os.confstr() or CS_PATH is not available
                path = os.defpath
        # bpo-35755: Don't use os.defpath if the PATH environment variable is
        # set to an empty string

    # PATH='' doesn't match, whereas PATH=':' looks in the current directory
    if not path:
        return None

    if use_bytes:
        path = fsencode(path)
        path = path.split(fsencode(os.pathsep))
    else:
        path = fsdecode(path)
        path = path.split(os.pathsep)

    if sys.platform == "win32":
        # The current directory takes precedence on Windows.
        curdir = os.curdir
        if use_bytes:
            curdir = fsencode(curdir)
        if curdir not in path:
            path.insert(0, curdir)

        # PATHEXT is necessary to check on Windows.
        pathext = os.environ.get("PATHEXT", "").split(os.pathsep)
        if use_bytes:
            pathext = [fsencode(ext) for ext in pathext]
        # See if the given file matches any of the expected path extensions.
        # This will allow us to short circuit when given "python.exe".
        # If it does match, only test that one, otherwise we have to try
        # others.
        if any(cmd.lower().endswith(ext.lower()) for ext in pathext):
            files = [cmd]
        else:
            files = [cmd + ext for ext in pathext]
    else:
        # On other platforms you don't have things like PATHEXT to tell you
        # what file suffixes are executable, so just pass on cmd as-is.
        files = [cmd]

    seen = set()
    for dir in path:
        normdir = os.path.normcase(dir)
        if not normdir in seen:
            seen.add(normdir)
            for thefile in files:
                name = os.path.join(dir, thefile)
                if _access_check(name, mode):
                    return name
    return None